Method of developing color film

ABSTRACT

Exposed color film is developed by first impregnating all color layers of the film emulsion with an inactively acidic developer solution so as to distribute the developer uniformly throughout, by removing excess developer solution from the surface of the film, and by then diffusing a strongly alkaline solution throughout the developer-impregnated emulsion layers so as to activate the developer in all layers without significantly altering the concentration of the developer in any layer.

0 United States Patent 11 1 1111 3,869,288

Godowsky Mar. 4, 1975 [54] METHOD OF DEVELOPING COLOR FILM 3,246,988 4/1966 Porter et a1 96/63 3,342,597 9/1967 Hamish et al 96/95 [761 lnvemo" 9P G0d0wsky, 19 Stony 3,425,832 2/1969 Bornemisza 96/50 R Pomt 6 Westport, Com 06880 3,759,712 9/1973 Kammerer et. a1. 96/50 R 22 F1 d: l 25, 1973 1 l e J y Primary E.\'aminerJ. Travis Brown 1 PP 382,470 Attorney, Agent, or FirnzStephen E. Feldman Related U.S. Application Data 57 ABSTRACT [63] Continuation of Ser. No. 118,515, Feb. 24, 1971, 1 I

abandoned Exposed color film is developed by first impregnating all color layers of the film emulsion with an inactively [52] U.S. Cl 96/22, 96/55, 96/95 acidic developer Solution 50 as to distribute the devei [51,] Int. Cl G03c 7/16 P uniformly throughout y removing excess devel- [58] Field of Search 96/22, 50 R, 63, 95, 55 9 Solution from the surface of film, n y then diffusing a strongly alkaline solution throughout the 5 References Ci d developer-impregnated emulsion layers so as to acti- UNITED STATES PATENTS vate the developer in all layers without significantly v 738 49s 4/194} M ta] 96/22 altering the concentration of the developer in any 8111165 C 2,860,977 11/1958 Tregillus 96/29 layer 2,920,960 l/l960 Bushell 96/63 8 Claims, No Drawings METHOD OF DEVELOPING COLOR FILM This is a X Continuation, of application Ser. No. 118,515; filed Feb. 24, 1971, now abandoned.

This invention relates to improvements in processing procedures for color film and color paper with advantages which the processing thus far have not possessed.

Conventional color film emulsions contain a plurality of layers each composed of their own respective color generative silver halide emulsion. Thus, when an exposed multi-layer color film or paper is immersed in a color developing solution, the developing solution immediately starts its work from the surface inward as it gradually diffuses throughout the layers. Inasmuch as developer penetration has to reach the middle and then the innermost layer only after working its way through the surface layer, as well as any intermediate layer, the inner layers suffer a lack of uniformity according to the work done outside their own stratum. This recognized uneveness of the penetration of the inner layers has been observed since the very beginning of multi-layer substractive color processing as the inter-image effect.

Efficient agitation helps reduce inter-image effect, but does not overcome it. In all continuous processing machines, black and white as well as color, some agitation has always been necessary to overcome directional developing effects. Without any agitation there is, besides this directional effect, also an area of increased density in the vicinity of perforation holes in the film due to added agitation by eddies caused by these perforations moving through the developing solution.

1 have now devised a method of developing such color film which imposes no rigid time limit for colorbalanced results. This method comprises subjecting the film emulsion to contact with an inactively-acidic aqueous color developer solution for a sufficient period of time for the developer solution to pervade the emulsion and thus establish a uniform concentration of the developer in and throughout each of the emulsion layers, and thereafter effecting permeation of the thus-treated emulsion with a strongly alkaline aqueous solution substantially exclusively by diffusion into said emulsion layers and thus rendering a substantial content of said developer in each layer reactive with respect to the exposed silver salt and coupler therein.

The color film to which the present invention is applicable is any of the conventional types having two or more color-sensitive emulsion layers, and it must be understood that the term film", as used herein and in the claims, includes paper-based emulsions and the like. The emulsions are made from gelatin or any other suitable polymer or carrier and can contain any conventional coupler of composition appropriate for the color to be developed in each specific layer. Yellow couplers, for example, include B-diketones, B-ketoacylamides, benzoylacetanilides, benziosoxazolones and compounds based on derivatives of active methylene groups. Magenta couplers include the cyanoacetyl types, derivatives of S-pyrazolones and the indozolones. Cyan couplers include acylamide-substituted phenols, derivatives of l-hydroxy-Z-naphthonic acid, and the like. As can be seen from the foregoing recitation, virtually any useful color coupler, which is capable of reacting with an oxidized conventional developer to form a coupler dye for the silver salt crystals in the emulsion, can be used in practicing the method inasmuch as the method of the invention is not based upon any specific chemistry but upon. a novel procedural concept of effecting contact between the developer and the emulsion containing the silver halide and the coupler.

The developer solution comprises any conventional aqueous developer solution. Sucl'n developers include N,N-diethyl-p-phenylenediamine, diethyl-ptolylenediamine, and the like. Again, the choice of developer used in the practice of the present invention is the same as for any conventional color development system. The concentration of the developer in conventional practice is about 6 grams per liter of solution, but in the practice of the present invention it has been found that such concentration, as well as those as high as 12 grams per liter and higher, can be used with advantage. The developer solution also contains the usual sodium'sulfite component, present in amount of about 8 gram per liter.

Pursuant to the method of the invention, the otherwise conventional color developer solution is rendered inactive with respect to silver development as well as with respect to color coupling by lowering its pH below 7, preferably to about 6.5 although lower pH values can be used. This acidity can be imparted by any appropriate acid or acid salt, but it is presently preferred to impart the required acidity by adding small amounts of sodium bisulfite to the developer until an acid pH, as indicated hereinbefore, is obtained.

Exposed color film is thus developed by the method of the present invention by first subjecting the film emulsion to contact with the inac'tively-acidic aqueous color developer solution for a sufficient period of time for the developer solution to pervade the emulsion and thus establish a uniform concentration of the developer in and throughout each of the color layers of the emulsion. This can be achieved simply by immersing or soaking the emulsion in the developer solution for sufficient time for the solution to penetrate all layers of the emulsion and to diffuse through, and thus pervade, each of the emulsion layers. Inasmuch as the developer solution is rendered inactive by its acidity, it does not significantly change in composition or strength, and therefore the developer which pervades the entire volume of each emulsion color layer is present therein in a uniform concentration as soon as diffusion stability has been attained.

Activation of the acidic developer solution throughout the thus-impregnated color layers of the emulsion is effected, pursuant to the invention, by rapid diffusion of a strongly alkaline activating solution into and throughout the developer-containing emulsion layers. This diffusion is an important characteristic of the method and must be distinguished from penetration of the developer-activating solution. into the developercontaining emulsion layers under such conditions as to wash a significant amount of the developer out of any of the emulsion layers. When permeation of the developer-activating solution is effected primarily by diffusion, the strongly alkaline character of this solution will change somewhat as its alkalinity is reduced by reaction with the acid component of the developer solution in each emulsion layer, but the reserve alkalinity of the activating solutions is sufficient to activate the developer uniformly throughout all emulsion layers. Moreover because of permeation of the developer-activating solution into the developer-containing layers by diffusion, that is without significant adverse agitation, the

activating solution does not wash any significant amount of developer out of any emulsion layer. Consequently, a uniform amount of developer is activated in each layer by the practice of the invention and color development is therefore not at the mercy of undesirable variations in developer concentration or of any of the other variables that have characterized depth development of multi-layer color film heretofore. Thus, it also becomes possible to choose not only balanced development of the layers but to keep the balance over a wider range of balanced densities of all color layers.

In order to achieve permeation of the developercontaining emulsion layers by diffusion pursuant to the invention, exposure of the developer-containing emulsion to the developer-activating solution should be carried out under conditions which avoid sugnificant agitation of the alkaline activating solution adjacent to the developer-impregnated emulsion. For example, the conventional practice of running film racks through a developing bath cannot be used effectively in practicing the invention because the sprocket openings along the sides of the film cause agitation of the bath. This type of agitation of the alkaline developer-activating solution used in the method of the invention causes a washing out of asignificant amount of developer from one or more of the emulsion layers and thus alters the degree of color development in those layers. Diffusion conditions, on the other hand, can be assured by passing the developer-impregnated emulsion through a spray, including a controlled system of fine mist or aerosol, of the alkaline developer-activating solution. The alkaline solution can also be applied to the developercontaining emulsion by an applicator, such as a series of rollers or belts, which make non-slipping contacts with the emulsion, the alkaline solution being continuously supplied to the rollers or belts. In addition, the concept of moving a loop of the film through a bath of the alkaline solution can be used provided that the emulsion side of the film is maintained in contact with an absorbent or porous layer of material which moves at the same speed as the film and thus precludes agitation of the alkaline solution adjacent the film emulsion, or it can be used when only the bottommost portion of each of a number of vertically oriented loops dips into a body of the alkaline solution so that the developerimpregnated emulsion is contacted with the alkaline solution only briefly at the bottom loops of the racks at repeated intervals and carries the solution quiescently during the remainder of its travel between these intervals. It will be understood, accordingly, that the contact between the alkaline developer-activating solution and the inactive developer-impregnated emulsion takes place, pursuant to the practice of my development method, in the absence of any physical pressure or action which would tend to physically displace any significant amount of the developer from the emulsion and actually takes place under conditions which are characterized primarily by rapid diffusion of OH ions into and throughout the developer-containing emulsion layers. The alkaline solution should have a pH higher than that of conventional single-developer solution, i.e. at least about 10.3 and preferably up to about 1 1.5. A still higher pH can be used up to the limit of any tendency of such higher pH solutions to affect adversely the composition of the film emulsion on other barrier layers,

and the like. Although strong alkalies such as sodium hydroxide can be used for this alkaline solution, the

presently preferred alkaline agent is predominately sodium carbonate. Other alkaline agents such as the strongly active alkyl amines can be used. The solution can also contain other conventional components such as a gelatin hardner and an anti-fogging agent such as sodium bromide and organic anti-foggants such as -nitrobenzimidazole, S-methylbenzotriazole and thioglycollic acid. Experience to date has indicated that the clarity of color obtained by the practice of the method of the invention permits the use of smaller than conventional amounts of such anti-fogging agents. Moreover. seasoning of the bath, as is customary with continuous developer baths used heretofore, appears to be wholly unnecessary.

The following specific example is illustrative but not limitative of the practice of the invention.

An inactive developer bath was prepared from 12 grams of diethyl-p-tolylenediamine hydrochloride, 16 grams of sodium sulfite and water to make up a volume of one liter. A sodium bisulfite solution was added to this solution by titration until the pH of the solution was lowered to 6.5. Camera-exposed Eastman Color Positive No. 5385 film was then immersed in this developer solution for about 2 minutes to insure complete pervasion of the solution throughout the film emulsion layers. The thus-treated film, after removal of excess surface developer solution, was then immersed, without agitation, in a strongly alkaline developer-activating solution composed of grams of sodium carbonate, 6.8 grams of sodium bromide, 1.8 gram of a gelatin hardner purchased on the market as Eastman Gel Hardner and sufficient water to form one liter. The film was left in this second bath for 6 minutes, then was rinsed with tap water and thereafter processed conventionally by bleaching, fixing and washing. The resulting film, compared to identical film exposed under identical conditions but developed by conventional commercial practice, was more clear and was characterized by improvement in color fidelity and brightness.

In further examples of the practice of the invention, the same exposed film, with the same immersion in the aforesaid developer and removal of excess developer solution on its surface, was treated with the aforesaid developeractivating solution by spraying the solution against the emulsion side of the film for 8 minutes in one test, and for 10 minutes in another test. The products of both tests were comparable in color fidelity and brightness to that of the first-mentioned example. The density of the film subjected to the 10 minute spray was, as would be expected, a little greater than that which was exposed to only the 8 minute spray. No noticeable change in color balance was apparent.

Although no explanation presently available can account for the improved color fidelity, brightness and image definition obtained by the practice of the present invention, it is possible that one reason for these improvements is the fact that in the prior art single bath developing process the oxidized developer can and does migrate from the developing centers, sometimes in extreme cases migrating as far as adjacent emulsion layers in spite of the presence of barriers or interlayers between the emulsion layers. In the present process, however, where no applied agitation is used or desired, and with the uniform saturation of all areas of all emulsion layers with a uniform concentration of activatible developer solution, the reaction centers around the reducing and coupling areas are more locally concentrated and therefore there is less wandering of oxidized developer. Accordingly, it will be understood that the method of the present invention is not only applicable to color film, which is characterized by a relatively thick emulsion composed of a plurality of emulsions and other strata, but is applicable to development of a non-color but thicker emulsion layer such, for example, as that used in tracing atomic particle tracks.

I claim:

l. The method of developing exposed color film having a photographic emulsion comprising a plurality of layers each containing a silver halide and a different color coupler which comprises subjecting the exposed film emulsion to contact with an inactively-acidic aqueous color developer solution for a sufficient period of time for the developer solution to pervade the emulsion and thus establish a uniform concentration of the developer in and throughout each of said layers, and immediately thereafter effecting permeation of the thustreated emulsion with a spray of small droplets of a strongly alkaline aqueous solution substantially exclusively by diffusion free from agitation into said emulsion layers and thus rendering substantially the entire content of said developer in each layer reactive with respect to the exposed silver salt and coupler therein.

2. The method according to claim 1 in which the alkaline aqueous solution has a pH of at least 10.3.

3. The method of claim 1 wherein the developer is so acidic that it remains inactive.

4. The method of claim 3 wherein the material which activates the developer is alkaline to cause the couplers to react in the emulsion.

5. The method of claim 4 wherein the developer in the emulsion developes the emulsion by diffusion.

6. The method of claim 5 wherein the developer has a pH below developability.

7. The method of claim 5 wherein the activating means has a pH sufficient to cause the couplers to react.

8. The method of claim 5 wherein the emulsion comprises three layers each containing a silver halide and a different color coupler. 

1. THE METHOD FOR DEVELOPING EXPOSED COLOR FILM HAVING A PHOTOGRAPHIC EMULSION COMPRISING A PLURALITY OF LAYERS EACH CONTAINING A SILVER HALIDE AND A DIFFERENT COLOR COUPLER WHICH COMPRISES SUBJECTING THE EXPOSED FILM EMULSION TO CONTACT WITH AN INACTIVELY-ACIDIC AQUEOUS COLOR DEVELOPER SOLUTION FOR A SUFFICIENT PERIOD OF TIME FOR THE DEVELOPER SOLUTION TO PERVADE THE EMULSION AND THUS ESTABLISH A UNIFORM CONCENTRATION OF THE DEVELOPER IN AND THROUGH EACH OF SAID LAYERS, AND IMMEDIATELY THEREAFTER EFFECTING PERMEATION OF THE THUSTREATED EMULSION WITH A SPRAY OF SMALL DROPLETS OF A STRONGLY ALKALINE AQUEOUS SOLUTION SUBSTANTIALLY EXCLUSIVELY BY DIFFUSION FREE FROM AGITATION INTO SAID EMULSION LAYERS AND THUS RENDERING SUBSTANTIALLY THE ENTIRE CONTENT OF SAID DEVELOPER IN EACH LAYER REACTIVE WITH RESPECTIVE TO THE EXPOSED SILVER SALT AND COUPLER THEREIN.
 2. The method according to claim 1 in which the alkaline aqueous solution has a pH of at least 10.3.
 3. The method of claim 1 wherein the developer is so acidic that it remains inactive.
 4. The method of claim 3 wherein the material which activates the developer is alkaline to cause the couplers to react in the emulsion.
 5. The method of claim 4 wherein the developer in the emulsion developes the emulsion by diffusion.
 6. The method of claim 5 wherein the developer has a pH below developability.
 7. The method of claim 5 wherein the activating means has a pH sufficient to cause the couplers to react.
 8. The method of claim 5 wherein the emulsion comprises three layers each containing a silver halide and a different color coupler. 